Jökull - 01.01.2012, Side 13

Sigurður Þórarinsson (1912–1983)
since the end of the glaciation (Figure 6). Below
the "Settlement layer" the rate of thickening had been
slow and even, but after that much more rapid, which
he attributed to deforestation and sheep-grazing.
At an international conference held in Iceland in
1980, entitled Tephra Studies as a Tool in Quaternary
Research, Sigurður gave an overview of the applica-
tion of tephrochronology in the country. He described
nine fields in which the method had come into use in
the 40 years since his first paper in 1940: volcanol-
ogy, archaeology, pollen-analytical studies of vegeta-
tion changes, fluvial erosion, wind erosion, studies of
periglacial phenomena, e.g. frost-crack polygons, dat-
ing of ice cores from glaciers, dating of glacier oscil-
lations, and establishing tephrochronological telecon-
nections between Iceland and other countries.
Later studies in volcanology
Sigurður Þórarinsson had estimated that on the aver-
age five years elapse between eruptions in Iceland.
During the 49 years of his professional life, 1934 to
1983, the average length between eruptions was 5.4
years. However, with the eruption in Askja 1961, a
period of frequent eruptions seems to have set in, and
during the 50 years between 1961 and 2011 the aver-
age length has been 3.6 years.
Askja 1961 was the second eruption Sigurður wit-
nessed, after Hekla 1947–1948, and until his death in
February 1983 he was not to miss a single one occur-
ring in Iceland. Although the 1961-eruption was, in
his own words, "small and insignificant" compared to
Hekla 1947–1948 and the great Askja 1875 eruption,
he followed it avidly and wrote about it in a scientific
journal as well as publishing a book for the general
public. Later, in 1967 Sigurður was the main geo-
logical guide when the Askja area was selected as a
training ground for the Apollo program to prepare as-
tronauts for the lunar missions.
The Surtsey eruption 1963–1967 was the first sub-
aquatic eruption studied in Iceland by scientists and as
such of great interest with reference to the countless
palagonite formations in the country. Sigurður was
very active in following its progress and already in
1964 he published a book and, with colleagues, two
scientific articles. The following years were to see
many more writings of his in various languages; in
Figure 6. Soil thickening at Vatnagardur, some 20 km west of Hekla, for 8000 years using tephrochronology.
In this section the break in slope is most noticeable at 1104 A.D. – Gjóskutímatal notað til að mæla jarðvegs-
þykknun 20 km vestan við Heklu í 8000 ár. Í þessu sniði eykst áfok fyrst verulega eftir 1104-gosið.
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